1. Field of the Invention
The present invention relates to an article transport apparatus in which articles, held by multiple article holding members installed at equal intervals, are rotated along an annular trackway (racetrack-type trackway) having a pair of parallel portions.
2. Background Art
Japanese Patent No. 4,190,692 discloses an article transport apparatus provided with a rotary transport mechanism and a reciprocating drive mechanism, in which the rotary transport mechanism rotationally transports multiple (or a plurality of) equidistantly installed article holding members in one direction along an annular trackway that includes a pair of parallel portions, and the reciprocating drive mechanism causes the entire rotary transport mechanism to reciprocate a predetermined distance along the parallel portions. In this transport apparatus, the rotary transport mechanism and the reciprocating drive mechanism are respectively provided with their own drive sources (servo motors). The article holding members have a travel velocity that is a combination of the velocity of rotary transport and the velocity of reciprocating motion, so that the article holding members travel, on one side of the parallel portion, in an intermittent manner, each time covering a distance that is an integral multiple (p×n) of the installation spacing p, and travel, on the other side of the parallel portion, in a continuous manner at a constant velocity.
In the above-described transport apparatus, articles are simultaneously supplied to a plurality of (n) article holding members when the article holding members come to a stop on one side of the parallel portion, and articles are sequentially discharged from the article holding members traveling in a continuous manner on the other side of the parallel portion. Conversely, articles can be simultaneously discharged from a plurality of (n) article holding members when the article holding members come to a stop in a parallel portion on one side, and articles can be sequentially supplied to article holding members traveling in a continuous manner along the parallel portion on the other side. In addition, by way of controlling the rotation of the two servo motors so as to change the velocity of reciprocating motion and/or the velocity of rotary transport of the rotary transport mechanism, it is possible that an arbitrary selection is made for operating patterns, such as the number (n) or the stop duration, etc., of the articles supplied or discharged at a single time.
In the transport apparatus disclosed in Japanese Patent No. 4,190,692, the article holding members travel along the parallel portion on the other side in a continuous manner at a constant velocity. Accordingly, when the apparatus is used as, for example, a bag transport apparatus in a bag-filling packaging machine, it is necessary that the packaging members (such as filling nozzles of a filling device, extracting members of an article extraction device, and the like), which directly act upon the articles, are moved so as to track (or follow) the continuous travel of the articles, when the articles (bags) are filled with materials to be packaged or when the articles are extracted from the transport apparatus at the parallel portion on the other side, etc. Therefore, sometimes, when the operating patterns of the transport apparatus are changed, it is necessary to also change the operating patterns of the packaging members (the velocity of travel, the timing of commencement of tracking, etc.). Such changes are, however, complicated and time-consuming operation. In addition, the tracking mechanisms used in the filling devices, article extraction devices, and the like become more complicated in order to permit tracking by the packaging members in various operating patterns, causing complexity and increase in size of the apparatus.